88 HARVESTING AND UTILIZING CORN 



preciable, but can be greatly reduced by taking proper precautions, 

 especially by making the silo absolutely tight, including the bottom, 

 and by covering the top with well-packed straw, stover, or other 

 materials. These losses are more than made up for by the increased 

 efficiency of the feed. 



" Ever since silage was first made, there has been doubt about the 

 causes of these important preservative changes in the fermentation 

 of milage. At first, bacteria were thought to be responsible, as in the 

 case of vinegar. Later, other investigators claimed that the cells of 

 the plant itself carried chemical substances called enzymes, which 

 were the only agents actually concerned. Other writers have taken 

 one side or the other on the subject. 



" The greater part of the past two years has been spent by the 

 writer in an effort to settle this much discussed question. The 

 results obtained show definitely that neither bacteria alone nor 

 plant enzymes alone are responsible for the fermentation of silage. 



" It has been found that a plant enzyme digests the starch and 

 gives a preliminary increase in some cases to the sugar content. 

 Another enzyme breaks down cane sugar into simple sugars. The 

 acid-forming bacteria are the agents which form most of the acid 

 from the sugar. This statement is supported by the fact that bac- 

 teriologists have found large numbers of acid-forming bacteria in 

 silage. Part of the alcohol is formed by the plant enzymes and 

 more alcohol is formed later by yeasts, which are microscopic one- 

 celled plants like bacteria. Some of the protein is digested by 

 plant enzymes and some by bacteria. Both 'plant enzymes and bac- 

 teria seem to have a share in the production of the heat, which 

 raises the temperature of the silage. The evolution of carbonic 

 acid gas, which is formed in such large quantities at the beginning 

 of the fermentation, seems to. be due largely to the plant enzymes, 

 although the bacteria and yeasts doubtless furnish part of it. 



" Direct evidence has been found of an enzyme called invertase 

 which hydrolyses or breaks down cane sugar, and of an enzyme 

 called zymase, which forms alcohol from sugar. Other investi- 

 gators have found enzymes in the corn plant which act on sugar 

 and on proteins. Enzymes of similar nature have been found in 



